Composite blade

ABSTRACT

Method of manufacturing a composite blade ( 300  through  313 ) having at least two blade portions ( 101, 201 ), for a tire curing mold having the steps of providing a first strip ( 100 ) of metallic material commonly used to form blades for tire curing molds; stamping or punching out from the strip various shapes to make main blade portions ( 101 ); providing a second strip ( 200 ) of metallic material; stamping or punching out from the second strip ( 200 ) a further set of blade portions ( 201 ) having a longitudinal and lateral dimensions which are preferably at most equal to those of the first blade portions ( 101 ), assembling at least one of the first and at least one of the second blade portions ( 201 ); and affixing the different blade portions ( 101, 201 ) together.

TECHNICAL FIELD

[0001] The present invention relates to blades for curing molds. Moreparticularly to composite type blades that have thicknesses which caneasily be tailored to the tire tread property requirements and a methodof fabricating such composite blades.

BACKGROUND OF THE INVENTION

[0002] Blades for tire curing molds are well known in the art of tiremanufacture. Such blades are conventionally made from a running lengthor strip of a metallic material such as steel, stainless steel or brass.The strip is generally about 0.4 mm to 1 mm thick and has a length ofabout 10 to 40 mm. Sometimes the strips are of solid form; other timesperforated strips are used to form the blades.

[0003] U.S. Pat. No. 3,880,020, a method and apparatus for makingblades, is disclosed which enables small quantity lots of a multiplicityof different styles of blades to be made rapidly and economically. Themethod and apparatus permits blades to be blanked out from the stack ofmaterial by a plurality of punch and die sets while the stock remainssecurely attached to an endless loop carrier. If so desired, a pluralityof sub-presses are used for forming bends in the blade.

[0004] In U. S. Pat. No. 3,581,535, a similar method and apparatus formaking blades is disclosed. The method and apparatus for making bladesfor use in tire molds includes piercing, notching, bending or otherwisealtering the shape of a free end of strip material by successivelypositioning the free end and a plurality of shape altering tools inoperative engagement and cutting off the formed blade from the free end.Bends, cuts, notches and holes are possible.

[0005] WO 99/21701 discloses a method of fabricating a composite bladeemploying the steps of forming a blade blank and encapsulating at leastone end in a second material by placing the end in a die and molding anenlarged cross-section of a second material around the end. Preferably,the second material is a powdered metal.

[0006] The blades create sipes in a tread during the vulcanization stepof a green tire in a curing mold. A sipe is a narrow groove or incisionin the tread and closes when located in the footprint, i.e., in thecontact patch of the tire tread with a flat surface at zero speed andunder normal load and inflation pressure. The sipes may extendcircumferentially or laterally about the tread in a straight, curved orzig-zag manner and may be as deep as the block and rib defining grooves.The sipes may pass through or cut one or both sides of the ribs andblocks or be confined to their interior. It is also known to have thesipes lying in planes which are not perpendicular to tangents to thesurface of the tread at their point of intersection. It is further knownto use sipes having a depth which varies along their length as well assipes which have varying thicknesses. However, the manufacturing of suchblades is expensive and lacks flexibility.

[0007] It is an object of the present invention to provide amanufacturing process for making a set of blades having differentthicknesses.

[0008] It is a further object of the present invention to provide amanufacturing process for making blades having varying thicknesses alongtheir length.

[0009] It is a further object of the present invention to provide amanufacturing process for making blades having varying thicknesses alongtheir depth.

[0010] It is a still further object of the present invention to providea mold for vulcanizing a tire as well as tire vulcanized in such mold.

SUMMARY OF THE INVENTION

[0011] The invention provides a method of manufacturing a compositeblade having at least two blade portions for a tire curing moldcomprising the steps of: providing a first strip of metallic materialcommonly used to form blades for tire curing molds; stamping or punchingout from the strip various shapes to make main blade portions; providinga second strip of metallic material; stamping or punching out from thesecond strip a set of second blade portions having longitudinal andlateral dimensions; assembling a main portion and at least one of thesecond blade portions; and affixing the different blade portionstogether to form the composite blade.

[0012] Preferably, the blade portions are affixed by the step of weldingor soldering the blade portions together.

[0013] The method further may have the steps of providing further stripsof metallic material; stamping or punching out from the further stripsfurther sets of blade portions having a longitudinal and lateraldimensions which are preferably at most equal to those of the main bladeportions; assembling a main and at least one of the second bladeportions together with at least one of the further portions; andaffixing the different blade portions together. A composite bladeobtained through the method is also disclosed.

[0014] In one embodiment the second strip of metallic material has thesame thickness as the first strip and the metal of the second strip ofmetallic material has the same composition as the first strip. Thecomposite blades may have any number of slots or cuts to form variousprojections.

[0015] A mold including the blade and a tire cured in the mold are alsodisclosed.

[0016] To acquaint persons skilled in the art, most closely related tothe instant invention, certain preferred embodiments are now describedwith reference to the annexed drawings. These embodiments areillustrative and can be modified in numerous ways within the scope ofthe invention defined in the claims.

BRIEF DESCRIPTION OF THE FIGURES

[0017]FIG. 1 is a view of a first strip used to form the main portion ofthe composite blade according to the invention;

[0018] FIGS. 2 to 4 show various main portions of differing shapes usedin assembling the composite blades according to the invention.

[0019]FIG. 5 is a view of a second strip used to form second portions ofthe composite blade according to the invention;

[0020] FIGS. 6 to 10 show various second blade portions of differingshapes used in assembling the blades according to the invention;

[0021] FIGS. 11 to 17 are views of substantially flat composite bladesobtained by using the process according to the invention;

[0022] FIGS. 18 to 20 are side views of composite blades having varyingdepths obtained by using the process according to the invention;

[0023] FIGS. 20 to 23 are top views on composite blades according to theinvention; and

[0024] FIGS. 24 to 25 are schematic sections across a block of rubberytread material.

DETAILED DESCRIPTION OF THE INVENTION

[0025] With reference to FIG. 1, a portion of a first strip (100) ofmetallic material commonly used to form blades for tire curing molds isshown. The resultant blades are stamped or punched out from the strip(100) and take various shapes as shown in FIGS. 2 to 4. The blades mayhave any number of slots (120) or cuts (121) to form the variousprojections (122). The blades may be wavy as shown in FIG. 3 or havebends at their extremities (see FIG. 4). These features are well knownin the tire building art and such blades are used as main portion of thecomposite blade according to the invention.

[0026] According to the invention and with reference to FIGS. 5 to 10, asecond strip (200) of metallic material commonly used to form blades fortire curing molds is stamped or punched to form a second set of bladeportions out from the strip (200) which may take various shapes as shownin FIGS. 6 to 10. This second strip (200) of metallic material may havethe same thickness as the first strip (100), a somewhat higher orsmaller thickness. Usually the thickness of the first strip (100) rangesbetween 0.3 and 1 mm and the thickness of the second strip (200) between0.3 and 0.8 mm. The metallic material of the second strip (200) may bethe same as the one of the first strip (100). Preferred metallicmaterial is steel because of its low cost. Further materials of interestare aluminum, nickel alloy, and titanium. Combinations of carbon steelconstituting the first strip (100) with titanium or other metalscontaining steel alloys constituting the second strip (200) would allowa great flexibility in the choice of the blade portion thicknesses.

[0027] The main blade portion (101) made out of the first strip (100) isusually at least partly anchored in the mold by holes (21) (see FIG. 2).This anchoring must be sufficient to insure that the composite blades donot pull out when the tread is extracted from the tire curing mold. Theblade portion (201) made out of the second strip (200) is or is notanchored in the mold, depending on the design of the blade.

[0028] The second blade portions (201) made out of the second strip(200) may take the shape of a rectangle (FIG. 6), parallelogram (FIG.7), triangle (FIG. 9), trapezoid (FIG. 10) and may basically have anygeometrical shape which is considered by a man skilled in the art toconfer favorable properties to the tire tread. They may be flat as shownin FIGS. 6 and 7, or they may be given a curved or wavy shape as shownin FIG. 8, depending on the fact that they will be assembled to acorresponding flat, curved or wavy main portion obtained out of thefirst strip (100). Alternatively the main portion (101) and the secondportion (201) may be given at first a flat shape and after assemblystamped in order to obtain the desired wavy, sinusoidal or crimped orsimilar shape.

[0029] After assembly, the main and second blade portions (101, 201) areaffixed together. This may be done by gluing using a high temperatureepoxy adhesive or a high temperature cement. Another possibility is tosubject the assembled portions to a combined compression and heattreatment. A still further possibility is to braze or solder the twoportions. The presently preferred way is to weld the different portionstogether along their lateral adjacent sides, or at multiple pointscalled “spot welding”.

[0030] The composite blades (300 through 312), according to theinvention, may be fabricated at low cost in a great variety of shapes.FIGS. 11 through 23 illustrate a few of these exemplary shapes,featuring different depths, widths and lengths. FIG. 11 shows a blade(300) providing a sipe having a greater width in its radially middleportion, FIG. 12 shows a blade (301) having substantially a width doubleto the one offered by single metallic strips (100) or (200). FIGS. 13,14 and 15 show blades (302, 303, 304) providing sipes with laterallystepped off widths, allowing to tailor the elastomeric block stiffnessto the requirements; such sipes influence locally transverse deformationof the blocks they are included in. FIG. 16 shows a blade (305)providing a sipe having on part of its lateral length and on part of itsradially inner portion, a higher width. FIG. 17 shows a blade (306)producing a sipe having on part of its length a higher width, whichlength decreases towards the tread surface. FIG. 18 shows a blade (307)providing a sipe having on both sides a higher width and a depthdecreasing from both sides towards the center. FIG. 19 shows a blade(308) providing a sipe having a first side a higher width and a depthdecreasing towards the second side. FIG. 20 shows a blade (309)providing a sipe having a lateral length decreasing radially towards thetread bottom and a higher sipe width portion with a width and lengthremaining constant.

[0031] It must be appreciated that some of the composite blades obtainedthrough the method according to the invention result in rathercomplicated blade layouts despite the fact that the manufacturing stepsare simple.

[0032] As more specifically illustrated in FIGS. 21 and 22, the blades(310, 311) obtained according to the method of the invention may includethe steps of bending. The bending step may take place before or afterassembly of the different blade portions. The blades may fuirther becrimped, notching or perforated before or after assembly. In FIG. 23 ablade (312) is shown where only part of the two metal sheets (101 and201) overlap. The sheets (101) and (201) can have the same height ordifferent heights.

[0033] With reference to FIGS. 24 and 25, the possibility of makinginterlocking sipes in the tread blocks is illustrated. For ease ofrepresentation, only one sipe per block (241, 251) is shown and theblock and grooves are not to scale. It is understood that a blockincludes usually several sipes. In the instant case, the further sipesmay have the same section than the one shown in the drawing. In FIG. 24a block (241) is defined by laterally and circumferentially extendinggrooves (242), wherefrom only one kind can be represented in thiscross-section. The block (241) includes sipe (245) which has in the caseof the drawing throughout its height, substantially uniform thickness.However, slightly above half-height, the sipe (245) shows a protrusion(243) on one side and a recess (247) on the other. Such sipe (245) iseasily obtained according to the inventive method by assembling to theradially outer part of a first side of a main portion (101) as shown inFIG. 2, a second blade portion (201) as shown in FIG. 6; a furthersimilar second blade portion (201), as shown in FIG. 6 is assembled tothe radially inner part of main portion (101).

[0034] It can be easily seen that if there is block deformation asindicated by arrow A, the protrusion (243) located on one side of thesipe, advances towards recess (247) on the other side of the sipe, untilit is in contact with such. Once in contact, protrusion (243) opposesany further deformation of the block (245). Opposite deformation doesnot result in such interlocking and the two adjacent sipe sidewalls mayslide along each other as far as allowed by the rigidity of the rubberymaterial and the forces applied thereto. It appears that such sipe isdirectional. It appears further that such interlocking stops when thetire is worn down to the protrusion (243). At that time the stiffness ofthe block has increased and a limiting of flexing is no more desired.

[0035] With reference to FIG. 25, the possibility of makingbi-directional interlocking sipes (255) in the tread blocks (251) isillustrated. Also, in this case only one sipe per block is shown forease of representation. Furthermore, the different elements are not toscale. In FIG. 25, a block (251) is defined by laterally andcircumferentially extending grooves (252). The block includes sipe (255)which has in the case of the drawing throughout its height,substantially uniform thickness. However, slightly above half-height,the sipe shows a protrusion (254) on one side and a recess (253) on theother. Such sipe is easily obtained according to the inventive method byassembling to a main portion (101) as shown in FIG. 2, two blade portionas shown in FIG. 6, to one side, and more specifically a first one (101)to its radially outer portion and a second one (201) to its radiallyinner portion, leaving a free portion in the middle of the main portion(101), which free portion defines in the cured tire the protrusion(254). On the middle portion of the other side of the main portion (101)a blade portion (201) as shown in FIG. 6 is assembled, which bladeportion defines the recess (253) in the cured tire.

[0036] It can be easily seen that if there is block deformation in adirection indicated by arrow A or in the opposite direction, protrudingrubbery material (254) will move towards recess (253) on the other sideof the sipe, until it nests into recess (253) opposing any furtherdeformation on the block (251). The amount of deformation required tohave such interlocking depends on the width of the sipe and on thelayout, mainly transverse dimensions, of the recess and the protrusion.It appears that such sipe has no directional effect in a new tire. Oncethe tire is about half worn down, the sipe will have substantially across-section which can be compared to that shown in FIG. 24 and itsbehavior will be, as explained in connection with FIG. 24.

[0037] In case of the sipes shown in FIGS. 24 and 25, the loss due towear of the non-directional interlocking (FIG. 24) or the change fromnon-directional to directional of the interlocking (FIG. 25) may becontrolled by giving the recess (247, 253) and similarly the protrusion(243, 254) a small inclination. This can easily be implemented byassembling second blade portions (201), as shown in FIG. 7 to the mainportion (101) of the composite blade (300 through 312).

What is claimed is:
 1. Method of manufacturing a composite blade havingat least two blade portions for a tire curing mold comprising the stepsof: providing a first strip of metallic material commonly used to formblades for tire curing molds; stamping or punching out from the stripvarious shapes to make main blade portions; providing a second strip ofmetallic material; stamping or punching out from the second strip a setof second blade portions having longitudinal and lateral dimensions;assembling a main portion and at least one of the second blade portions;and affixing the different blade portions together to form the compositeblade.
 2. The method according to claim 1 wherein the blade portions areaffixed by the steps of welding or soldering the blade portionstogether.
 3. The method according to claim 1 comprising the further stepof providing further strips of metallic material; stamping or punchingout from the further strips sets of blade portions having a longitudinaland lateral dimensions which are preferably at most equal to those ofthe main blade portions; assembling a main and at least one of thesecond blade portions together with at least one of the furtherportions; and affixing the different blade portions together.
 4. Acomposite blade obtained through the method of any of claim
 1. 5. Thecomposite blade according to claim 4 wherein the second strip ofmetallic material has the same thickness as the first strip.
 6. Thecomposite blade according to claim 4 wherein the metal of the secondstrip of metallic material has the same compositions as the first strip.7. The composite blade according to claim 4 wherein the composite bladeshave any number of slots or cuts to form various projections.
 8. A moldincluding a blade according to claim
 1. 9. Tire cured in a moldaccording to claim 1.